Our health depends on vitamins, and to understand that dependency, it helps to understand the history of vitamins. As I wrote in an article in Science Times this week, our ancestors have probably needed vitamins for billions of years. By studying how we and other species make vitamins, scientists hope to find new ways to keep us healthy — perhaps even by using vitamins as a weapon against our enemies.

There are two ways of getting those vitamins: making them or eating them. Our microbial ancestors probably made many of their vitamins, but later much of that ability was lost. Our primate ancestors lost the ability to make their own vitamin C about 60 million years ago.

Those ancestors didn’t need to make vitamin C, however, because they regularly ate fruit. More recently, our hunter-gatherer ancestors got an abundant supply of vitamins from the game they killed and the plants they collected. But with the rise of agriculture, people began to eat more vitamin-poor starches like wheat and corn. And as we’ve transformed our diet even further, we’ve put ourselves at risk of vitamin-related diseases.

In the mid-1800s, for example, manufacturers began processing rice in steam-powered mills, which stripped off their vitamin-rich outer layer. As white rice became increasingly common, so did a disease called beriberi, which causes people to lose the feeling in their legs and begin to have trouble walking.

Beriberi baffled scientists for decades. In the 1880s, a scientist named Christiaan Eijkman found that chickens could develop a beriberi-like condition and started studying them to find the cause of the disease. For years he was convinced some kind of bacteria was to blame. But then he discovered that a flock of sick chickens suddenly recovered from beriberi-like symptoms.

It turned out that the chickens had initially been fed on leftover rice from the military hospital in the Netherlands where Dr. Eijkman did his research. “Then the cook was replaced and his successor refused to allow military rice to be taken for civilian chickens,” Dr. Eijkman later explained when he accepted the 1929 Nobel Prize in Physiology or Medicine for his research.

Once the birds started eating unprocessed rice, they quickly recovered. Dr. Eijkman realized that something essential to life must be in the outer layer of rice. In 1912, the Polish-born biochemist Casimir Funk called this mysterious compound a “vital amine,” which came to be shortened to vitamin. Later, researchers discovered that the outer layer of rice is rich in vitamin B1 (also known as thiamine).

In the century since Mr. Funk recognized vitamins, they’ve become a big business.

In the United States alone, annual sales of multivitamin and mineral supplements total $12.5 billion. Yet a balanced diet will generally provide a sufficient supply of vitamins, and there’s little evidence that extra vitamins in supplements do much good. For example, a 2013 review of studies involving 294,718 people found no evidence that vitamin supplements prevent cardiovascular disease. (Studies have also revealed important exceptions — pregnant women, for example, benefit from an extra supply of vitamin B9, also known as folic acid.)

While vitamin supplements may not do much good in countries where malnutrition is not a serious issue, vitamin deficiency still remains a threat in many places. Billions of people depend on vitamin-poor staple crops like rice and cassava. Vitamin A deficiency, for example, robs the eye of its light-sensing molecules, and has been estimated to cause 500,000 cases of blindness in children worldwide. It also weakens our defenses against infections, leading to 700,000 deaths.

“It’s a major global problem,” said Teresa B. Fitzpatrick, a botanist at the University of Geneva.

A better variety of foods could reduce vitamin deficiencies, but Dr. Fitzgerald is skeptical that that’s the best strategy. “Right now it’s not a practical solution,” Dr. Fitzgerald said.

Instead, she argues for altering staple crops. “This is what they eat everyday,” she said.

Understanding the evolutionary biology of vitamins can help scientists make those changes. Plants, for example, have evolved different pathways to make various vitamins they need to grow. It’s only in the past few years that scientists have mapped many of those pathways. That knowledge may allow scientists to increase the production of vitamins in crops through breeding, or by engineering them by moving genes from one plant to another.

“Before, it just couldn’t be done,” Dr. Fitzgerald said.

There’s another way that studying vitamins can improve human health: by revealing the vulnerabilities of the parasites that infect us.

Malaria, for example, is caused by a single-celled parasite called Plasmodium that invades red blood cells. Like us, Plasmodium needs its vitamins — some of which it makes for itself, and some of which it steals from us.

Kevin Saliba, a biochemist at Australian National University, and his colleagues are developing compounds that mimic vitamins. Plasmodium grabs them as if they were real vitamins, but once it tries to use them, they fail to carry out the chemical reactions the parasite depends on. In Dr. Saliba’s recent experiments, reported in the journal Plos One, this trickery leads to the death of Plasmodium.

“It’s still early days,” said Dr. Saliba, so it’s too soon to know whether this vitamin sabotage could be a cure for malaria.

But if the research does prove to be successful, it will be a delicious turnabout. We may not be able to escape our four-billion-year thrall to vitamins. But neither can our enemies.

Copyright 2013 The New York Times Company. Reproduced with permission.